Ravenor is a quick to learn, easy to use, not too complex hero. He is best at dealing magic damage in an area. But he is not a nuker. His spells are powerful when applied over and over to his target. He is fast and hard hitting, but a tends to be fragile, so be careful early on. He has potential to carry and can be a good ganker. And he is ugly. Let’s have a look at his abilities.
Ball Lightning. Ravenor shoots a lightning ball at the desired direction. The projectile moves slowly forward and hits the first enemy hero it comes in contact with. It doesn’t damage creeps and it goes through them. Once it hits an enemy, Ravenor is able to blink right next to him by activating the spell again. His appearance on the new spot stuns and damages everyone who is near.
Storm Blades. Upon activation it charges up Ravenor’s attack with additional magic damage and increases his attack speed. All nearby enemy units will also be hit by a lightning and will take damage.
Electrical Feedback. This causes every enemy who attacks Ravenor to take magical damage in return. In addition, two more enemies who are nearby will also take damage.
Power Overwhelming. The ultimate ability is passive. It is charged-based. Charges are gained every time when Ravenor deals magic damage to an enemy. For a creep he gets 1 charge and for a hero he gets 8 charges. Each charge gives him 1 movement speed and 1 magic damage to his auto attacks. The maximum is 120 charges, which means that at Ravenor eventually gets 120 movement speed and 120 magic damage.
One way is to max his Ball Lightning first. It is his best offensive ability with the largest amount of damage. I would recommend to put only one point on it at first and prioritize the other two abilities. This way you will still be able to take advantage of the gank, initiation and chase potential of Lighting Ball, while at the same time you will be strong enough to be a treat to many heroes in one-on-one battles. More importantly, with Storm Blades and Electrical Feedback combined, your farming ability increases drastically. Being overfarmed will let you dominate later. I doubt that anyone would underestimate the advantage of Power Overwhelming. Take it whenever possible. Stats are kept for last.
Steamboots to increase survivability. Icebrand will look good on him next. Or Nullfire blade. A Null stone will probably be needed to avoid being disabled. To increase damage potential Hellflower is perfect. A Frostwolf skull is of course always a good choice.